This invention relates to a production control device. More particularly, but not by way of limitation, this invention relates to a production control device used in the production of hydrocarbons from subterranean reservoirs and its method of use.
In the production of hydrocarbons from a well, operators may find it necessary to either open a port within a tubular string or close a port within a tubular string. A valve placed in a tubular string can be used to establish communication with the reservoir, or alternatively, to shut-off communication with the reservoir. Several devices have been developed over the years to accomplish the opening and/or closing of ports. These devices are generally known as sliding sleeves due to the ability to shift an inner sleeve from a first position to a second position. Sliding sleeves are commercially available from several vendors. One type of sliding sleeve that is commercially available is sold under the name “Otis DuraSleeve” and may be purchased from Halliburton Corporation.
One of the major problems with these prior art down hole devices is the seals. After the sleeve has been shifted from the closed position to the open position with a differential pressure greater than 2500 psi, the valves would leak when shifted back to the closed position. The cause of the failure is generally cutting or clipping of the seals as the equalizing ports and the sleeve production ports pass under the seals. The cutting is a result of a change in the physical properties of the seals at temperatures above 250 degrees Fahrenheit. For instance, the tensile strength of a Viton seal ring (Viton is a trademark of Dupont Corporation) at 70 degrees Fahrenheit is between 1250 psi to 2000 psi; however, at 210 degrees Fahrenheit, the tensile strength is less than 200 psi. The tensile strength of a Teflon seal ring (Teflon is a trademark of Dupont Corporation) at 70 degrees Fahrenheit is between 2500 psi to 3000 psi; however, at 210 degrees Fahrenheit, the tensile strength is less than 500 psi.
Therefore, there is a need for a device that can be selectively opened and closed in a well. There is also a need for a device that can be shifted from a closed position to an open position, or alternatively from an open position to a closed position, without harming the seal assembly. There is also a need for a seal assembly within a down hole device that will continue to provide for a seal after multiple openings and closings of the down hole device. These, as well as many other needs, will be met by the following invention.